PETG Stringing, Warping, and Adhesion Fixes
Most PETG printing issues stem from one of three problems: thin strings between parts, corners lifting off the build plate, or the print detaching from the bed entirely. Each issue has a distinct cause, and none are resolved by adjusting retraction values alone. This guide walks you through diagnosing each failure mode in order, so you can address the root cause instead of the symptom.
Start Here: Dry the Filament First
PETG is hygroscopic, meaning it absorbs moisture easily. Wet filament can cause stringing, nozzle popping, and inconsistent layer adhesion, making it appear as if the problem is with the print settings. If your filament has been exposed to air for more than a week in a room with humidity above roughly 40%, dry it for 4 to 6 hours at 60 to 65°C before making any other adjustments. Skipping this step is the most common reason why changes to settings don't seem to work.
Why This Matters First
Wet PETG exhibits the same symptoms as poor retraction or an overly hot nozzle. Eliminating moisture before tweaking slicer settings saves hours of troubleshooting incorrect fixes.
Stringing: Hair-like Strands Between Parts
PETG tends to ooze more than PLA because it remains soft over a broader temperature range, leading to continuous flow during travel moves rather than freezing off cleanly. Once moisture is ruled out, follow these steps in order.
Nozzle Temperature Too High
Printing at the upper end of PETG's temperature range makes the filament runnier than necessary, resulting in more ooze during travel.
Fix: Gradually lower the temperature by 5°C increments, typically starting around 240°C, until stringing stops without compromising layer adhesion.
Retraction Under-tuned
PETG requires less retraction on direct drive printers and more on Bowden setups. The optimal retraction distance varies by printer.
Fix: Test retraction settings with a retraction tower. For direct drive, start around 1.0 to 1.2mm at 25 to 35mm/s, and for Bowden, start at 5 to 7mm at 35 to 45mm/s, then adjust accordingly.
Travel Speed Too Slow
Longer dwell times between features allow more time for PETG to ooze from the nozzle.
Fix: Increase travel speed, as most slicers default to speeds lower than what the printer can safely handle for non-printing moves.
Warping: Corners Lifting Off the Bed
PETG warps less than ABS but more than PLA, and it primarily affects larger, flatter parts where corners cool and shrink faster than the center holds them down.
Bed Temperature Too Low or Uneven
A cooler bed, or one with cold spots, causes the first layers to contract unevenly as they cool.
Fix: Maintain a bed temperature of 70 to 85°C throughout the entire print and ensure consistent temperature across the bed.
Cooling Fan Running Too Early
Aggressive cooling of the first few layers locks in the temperature difference between the corners and the bed before adhesion sets.
Fix: Keep the fan off for the first 3 to 4 layers, then gradually increase to 20 to 50% for the remainder of the print.
No Brim on Large or Thin Parts
Parts with a small footprint relative to their height have less surface area to resist the shrinkage pulling at the corners.
Fix: Add a 5 to 10mm brim on any part wider than it is tall or with sharp outer corners.
Not Sticking: The Print Won't Stay Down
This issue contrasts with warping, where the part detaches entirely from the bed, usually early in the print, rather than lifting at the corners.
First Layer Printed Too Fast
A quickly laid first layer doesn't have enough time to bond properly with the heated bed.
Fix: Print the first layer at 15 to 25mm/s, well below your normal print speed.
Dirty or Incompatible Bed Surface
Oils from handling the plate or a surface PETG doesn't bond well with can produce poor adhesion regardless of temperature settings.
Fix: Clean the plate with isopropyl alcohol before every print. On smooth PEI or glass, a thin layer of glue stick can help PETG grip.
Bed Too Cool for the Surface in Use
Textured PEI and bare glass require different bed temperatures to achieve the same grip from PETG.
Fix: Start at 75°C on textured PEI, or 80°C on glass, and adjust in small increments rather than jumping to the maximum temperature.
Quick Diagnosis
If you only have time to check one thing, use the following table to match your symptom.
| Symptom | Check First |
|---|---|
| Fine hair-like strings everywhere | Dry the filament, then lower nozzle temperature 5°C |
| Popping sounds while printing | Filament is wet, dry it before anything else |
| Corners curling up mid-print | Raise bed temperature, delay cooling fan, add a brim |
| Whole part pops off early | Slow the first layer, clean the bed, raise bed temperature slightly |
If You're Still Fighting the Material
Some of this comes down to the spool itself. Consistency between batches varies more with PETG than with PLA, so a brand that prints cleanly on one printer can string or warp on another. If you've addressed moisture, temperature, retraction, and bed preparation and it's still problematic, it might be worth trying a different brand rather than continuing to tweak settings. The PETG filament guide covers the full settings range and where PETG fits against PLA and ABS, and if the part needs to live outdoors, the best filament for outdoor use guide covers when PETG is good enough versus when to step up to ASA.
Compare PETG Prices by Brand
If it's time to try a different spool, compare live PETG listings by brand, weight, and price per kg to find the best value.
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